title: Crystal structures of EF-G-ribosome complexes trapped in intermediate states of translocation.
abstract: Translocation of messenger and transfer RNA (mRNA and tRNA) through the ribosome is a crucial step in protein synthesis, whose mechanism is not yet understood. The crystal structures of three Thermus ribosome-tRNA-mRNA-EF-G complexes trapped with β,γ-imidoguanosine 5'-triphosphate (GDPNP) or fusidic acid reveal conformational changes occurring during intermediate states of translocation, including large-scale rotation of the 30S subunit head and body. In all complexes, the tRNA acceptor ends occupy the 50S subunit E site, while their anticodon stem loops move with the head of the 30S subunit to positions between the P and E sites, forming chimeric intermediate states. Two universally conserved bases of 16S ribosomal RNA that intercalate between bases of the mRNA may act as "pawls" of a translocational ratchet. These findings provide new insights into the molecular mechanism of ribosomal translocation.
authors.affiliation: Center for Molecular Biology of RNA and Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Laura
authors.initials: L
authors.lastname: Lancaster
authors.forename: John Paul
authors.initials: JP
authors.lastname: Donohue
authors.forename: Harry F
authors.initials: HF
authors.lastname: Noller
mesh_terms: D018360:Crystallography, X-Ray; D005672:Fusidic Acid / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry; D020653:Peptide Elongation Factor G / Q000737:chemistry*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012333:RNA, Messenger / Q000737:chemistry; D012343:RNA, Transfer / Q000737:chemistry; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry*; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: C503923:GDPNP compound; D020653:Peptide Elongation Factor G; D012333:RNA, Messenger; D005672:Fusidic Acid; D006160:Guanosine Triphosphate; D012343:RNA, Transfer